Any plant or
animal that is not native to your region is considered an exotic species.

All
most all aquarium fishes and plants available for sale in national pet shops are
exotic and are imported predominantly from farms located elsewhere, but the
original ones were collected out of Europe, specially in Central and South
America, Africa, or Southeast Asia.

Each
year, over 2000 species, representing nearly 150 million exotic freshwater
and marine fishes, are imported just into the United States for use in the
aquarium trade.

Europe and Japan probably fallow this income, however on a
different proportion.

A
massive income of potential invasive organisms is a daily threat in those
countries where aquarium is a popular hobby.

Most
hazard species will not resist to the first winter lower temperatures here
in Europe, but
their impact on local ecosystem can be potentially dreadful for years after
a single summer season.

Potential problems

Unfortunately, a number
of exotic fishes are released into the wild each year.

Hobbyists
may not be able to take their fish with them when they move, so relasing the
pets in natural waters is a hypotetical fast and nice solution.

Others
simply may have lost interest in maintaining some species or the aquarium
itself.

Fish
may also be released if they outgrow the tank capacity or if they appear to
be in poor health.

Whatever the reason it can be considered, releasing
exotic fish and aquatic plants into local waters is not a good idea at all.

As
in many other countries, in Portugal that it is an illegal practice .

You
can read from the published document on the legislation issue all the
details, ( unfortunately still only in Portuguese by now ).

But
there are sound biological reasons, too.

Released
fish will be physiologically stressed upon introduction to a different
environment.

These
newly unconfined animals will be susceptible to parasites and diseases from
the wild or can pass on fatal unknown pathological agents to the new
ecosystem.

Native
predators such as larger fish, fish-eating birds, or water snakes and
mammals that prey on fish might attack them.

For
the environment it can be dramatic.

If
exotic species can survive and reproduce, once establish they are difficult,
if not impossible to control or eradicate.

Invasive
plants and animals are a major threat to natural ecosystems and their
species, second only to direct destruction of habitats by humans.

Non-indigenous
aquatic plants can become a pest out of control in no time. They can
colonize water bodies, competing for space and light, eliminating original
aquatic flora and alter radically the environment.

Floating aquatic plants,
for instance, can grow as much as limiting boat traffic, swimming and
fishing, preventing light and oxygen from reaching the water column.

Introduced
fish often cause changes in the existing aquatic original faunal makeup and
food chains, through competition with native species or predation on them,
as well as through overcrowding or aggressive behaviour.

They
may contaminate native fish with exotic parasites or diseases to which local
fauna isn’t biologically prepared to respond against.

An
exotic may also affect the genetics of native species by hybridizing with
them in the presence of close species.

Even
the simple relocation of a few individuals from one hydrographical basin to
another, inside their natural distribution, can cause harm to the gene
diversity of the entire population.

Sole
species may pose a physical or public health threat, such as some rare
freshwater dangerous and noxious introduced fish.

Current situation

Currently, in
Portugal there are 14 introduced freshwater species for a total of about 57.

In
many other European countries the situation is far from be very dissimilar.

On
the other side of the Atlantic, at least 185 different species of exotic
fishes have been caught in open waters of the United States, and 75 of these
are known to have established breeding populations. Over half of these
introductions are due to the release or escape of aquarium fishes.

Because
many of these fishes are native to tropical regions of the world, their
thermal requirements usually prevent them from surviving in temperate areas.

In
the U.S., therefore, most introduced fishes have become established in
Florida, Texas, and the Southwest. Examples include a number of cichlid, (
Cichlidae Family ) and livebearer Cyprinodontiformes, such as Swordtails (Xiphophorus helleri ), Platies ( Xiphophorus maculatus ) and Mollies ( Poecilia sp ).

The goldfish, a native of China, is one of the few
examples of a temperate aquarium species that is established throughout the
U.S.

What can someone
do to avoid introductions ?

Alternatives to release, avoiding subject the fish to potentially harmful
environmental conditions or risking prospective remarkable ecological and
dreadful consequences are not very widespread yet, but there are optional
means for disposing of unwanted pet fish.

Merely
as a starting point there are a few possibilities to take in consideration
while dealing with healthy fish too numerous or too big for the aquarium.
One last hypothetical reason can even be those fish viewed as discarded pet
as well.

In
any of this odds here are some potential solutions :

a) Return it to a
local pet shop for resale or trade.

b)
Give it to another hobbyist, an aquarium in a professional office, a museum,
or to a public aquarium or zoological park.

c)
Donate it to a public or private institution, such as schools, hospitals,
prisons, enterprises, clubs, fire departments and other places where
aquariums are kept.

If these options
are not available, or fish are agonising and perception of recovery is
almost null, a veterinarian or fishery biologist can euthanize it ( put it
to sleep ) with anaesthetic.

You
can also do this at home by placing the fish in a container of water and
putting it into the freezer.

Because cold temperature is a natural
anaesthetic to tropical fishes, this is considered a very humane method of
euthanasia, while doesn't work well with all species.

Some
pet shops also may be able to assist you if euthanasia is the option you
choose.

Feeding
other piscivorous fish with live prey is an ultimate option that many
persons are reluctant to accept when time to deal with unwanted fish arises.

An
excellent discussion of fish euthanasia was published in the September 1988
issue of Tropical Fish Hobbyist. This magazine is probably not very easy to
find outside the United States, but it may be available through pet shops or
at your local library with luck.

If
you must give up your pet fish, please consider its well-being and its
potential impact on the environment.

Do
not release exotic fish and plants into a natural body of water or even to
an artificial water environment. In the most unsuspicious places there is
still a continuous risk of late dispersal to the wild by countless ways,
without disregard even human action.

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